Spring cushioning devices



April 17, 1962 A. H. PERRY SPRING CUSHIONING DEVICES 2 Sheets-Sheet 2 Filed Oct. 31. 1960 v Art/nu- Hereri Percy B %e ttorneys United States idatent 3,030,097 SPRING CUSHIONING DEVICES Arthur Herbert Perry, West Brornwich, England, assignor to George Salter & Company Limited, West Bromwich, England, a British company Filed Oct. 31, 1960, Ser. No. 66,035 3 Claims. (Cl. 267-1) This invention relates to spring cushioning devices, and more particularly, to a novel construction of spring cushioning device intended for use in the packaging of delicate material or apparatus requiring protection from external shock forces. The essential features of the invention may be advantageously employed in devices intended for relatively light duty cushioning.

According to the present invention, a spring cushioning device is in the form of a self-contained unit adapted to be interposed between an outer packaging container and abody within the container, and it comprises two spacedapart relatively-movable pressure plates, spring means between said plates and retaining means, independent of said spring means, arranged to prevent complete separation of the pressure plates, said spring means including a plurality of resilient torsion rods associated with one pressure plate, each torsion rod carrying at one end a lever arm extending laterally in an inclined direction towards the second plate, the outer ends of said lever arms being arranged to bear upon said second plate whereby movement of the two plates under load towards one another will cause said lever arms to be deflected and to apply a twisting couple to the rods and generate a torsional stress therein, the other end of each of said rods being restrained from twisting in the same sense as the applied couple by a second laterally-extending restraining lever arm, the arrangement being such that the outer ends of the firstnamed lever arms move freely in contact with the second pressure plate during deflection under load so that the efiective length of these arms progressively increase.

The torsion rods and respective associated lever arms are preferably integral and for a light-duty device they may be formed as single spring elements from single lengths of spring steel wire. Furthermore, pairs of torsion rods extending laterally with respect to one another may be made integral as parts of single spring elements, each torsion rod serving as the restraining lever arm of the other. Several torsion rods are also preferably arranged to lie together and parallel to one another to form a group, and in some cases it may be preferred for a series of these groups to be arranged with dilierent orientations so that load between the two pressure plates is spread evenly and efficiently. The torsion rods may be secured to the one press plate by a clamping plate or by suitable bridge pieces.

The means for preventing complete separation of the pressure plates, may in many cases conveniently consist of a flexible thread or cable anchored at each end to one plate and embracing the other plate.

The invention will now be more particularly described I by way of example in connection with embodiments illustrated in the accompanying drawing and intended for use as light duty cushioning devices in packaging. In said drawing,

FIGURE 1 is a side elevational view of one form of cushioning device in accordance with the invention, shown interposed between two members representing the walls of inner and outer packaging containers;

FIGURE 2 shows on a larger scale a cross-section on line II-II of FIGURE 1, a compressed state of the device being indicated in broken lines;

FIGURE 3 is a perspective view of one end of the device;

FIGURE 4 is a section on line IV-IV of FIGURE 1, part being broken away to show the arrangement of groups of spring elements;

FIGURE 5 is a perspective view of a single constituent spring element; 2

FIGURE 6 shows in perspective a modification in which part is broken away, and

FIGURES 7 and 8 represent side elevational and end views respectively of a further modification.

The device shown in FIGURES 1 to 5 is in the form of a self-contained unit and comprises essentially two flat-sheetmetal pressure plates 1 and 2 which are of rectangular form and are normally spaced apart, one above the other, and between these plates 1 and 2 is disposed a plurality of spring elements 3 constituting torsion bars and associated lever arms in accordance with the invention.

Each spring element 3 is formed from a single length of spring steel wire which is bent at the middle through a right angle to form two main arms 4, 4 each of which is further bent towards its outer ends to produce integral subsidiary end arms 5, 5 each lying in a plane perpendicular to the direction of the respective main arm 4 or 4 from which it is formed, these subsidiary arms 5, 5 being slightly inclined towards one another and the tips 6 of their free ends being bent over.

The spring elements 3 are assembled in a series of group upon the pressure plate 1, the main arms 4, 4 of each element lying flat upon the surface of the plate 1, and the subsidiary arms 5, 5 extending in an inclined direction towards the other plate 2. It will be clear from the drawing that each group contains several of the spring elements 3 which are nested together with the right-angle corner at the junction of the two main arms 4, 4 of one element fitting into the corresponding corner of an adjacent element, corresponding main arms 4 or 4 of adjacent elements 3 lying side-by-side. Also, in this specific embodiment, the spring elements 3 of the several groups are all arranged symmetrically along the major axis of the pressure plates 1 and 2. The spring elements 3 are conveniently held in place by means of a clamping plate 7 secured to the plate 1 by lugs 8 passing between the difierent groups of elements.

The two plates 1 and 2 are prevented from complete separation by means of a retaining flexible thread or cable 9 which is conveniently in one piece and is anchored at its ends to the pressure plate 2 (see FIGURE 3). This thread or cable 9 is passed through holes around the edges of the two plates 1 and 2 so as to embrace them both, and it is of such a length as to draw the said plates together so that the free bent-over tips 6 of the subsidiary arms 5, 5 of the spring elements 3 carried by the one plate I bear against the opposed surface of the second plate 2.

Each of the subsidiary arms 5 thus forms a lever arm which is deflected as the plates 1 and 2 are moved further together (see FIGURE 2) and applies a twisting couple e9 to the respective main arm 4 of which it forms an extension. The other end of this main arm 4 is restrained from twisting, however, by the second main arm 4 of the spring element 3 in question, which extends laterally and is held by the clamping plate 7. This second main arm 4 therefore forms a second lever arm as far as the first main arm 4 is concerned, opposing the twisting couple applied by the deflected lever arm 5 at the outer end. The first main arm 4 is therefore stressed torsionally and forms a torsion bar. Similarly, with this particular form of the spring elements 3, the first main arm 4 also functions as a restraining lever arm as far as the second main arm 4 is concerned, so that the latter is also stressed torsionally by similar deflection of the subsidiary lever arm 5 at its outer end, and forms a second torsion bar.

In use, these cushioning devices are used as separators between an outer packaging container and a body contained therein or between the walls of inner and outer containers (indicated respectively at 11 and 12 in FIG- URE 1). Any desired number of these devices may be employed, and preferably they are inserted with a small degree of initial compression.

The greater the pressure exerted between the plates 1 and 2 tending to compress them together, the greater the deflection of the subsidiary lever arms 5, 5 and the tips 6 at the free outer ends of the latter move laterally across the surface of the plate 2 upon which they bear. This movement is facilitated by the bending-over of the tips 6, as previously described.

The effective length of the subsidiary lever arms 5 and 5 is, of course, equal to the distance between parallel planes perpendicular to the plates 1 and 2 and passing respectively through the point of contact of the outer end 6 of the lever arm 5 or 5 with the plate 2 and through the axis of the associated main arm or torsion bar 4 or 4 The effective length of each subsidiary lever arm 5, 5 therefore increases as its deflection increases, and this enables a load/deflection characteristic to be obtained such there will be only a small movement of the two pressure plates towards each other until a predetermined load between them is reached, but thereafter, small further increases in load will cause relatively large movements of the pressure plates with corresponding relatively large absorptions of energy. This is a very desirable characteristic of a spring cushioning device of this character since it allows for the maximum absorption of energy below a maximum permitted safe load for which it is designed.

Since spring cushioning devices in accordance with the invention may have an all-metal construction, the possibility of deterioration due to adverse climatic conditions can be eliminated which is an important advantage over known cushioning materials, such as resilient plastics or rubber, which are often employed.

In FIGURE 6 is shown a modification in which two pressure plates 1 and 2 are separated by spring elements 3 of similar form to those already described, but in this case, these spring elements 3 are arranged in two groups having different orientations, the one set of main arms of the one group lying parallel to and interleaved with the one set of main arms of the other group, the main arms of the groups of spring elements collectively extending in the directions of the three sides of a square. The spring elements 3 are conveniently held in place by means of U-shaped staples 14 which bridge each set of main arms and the two plates are held together by a thread 9 as in the first embodiment.

The modified form shown in FIGURES 7 and 8 is basically the same as the embodiment first described with reference to FIGURES 1 to 5 and the same reference numerals are used for corresponding parts. The row of spring elements 3 seating upon the pressure plate 1, however, are held in place by a clamping plate 7 upon which is mounted a second similar row of spring elements 3 each of which is turned round through with respect to the spring elements of the lower row so that the lever arms 5 and 5 are inclined in the opposite direction. The second row of spring elements is held in place by a second clamping plate 7*, the clamping plate 7 carrying integral lugs 8 and 8 for securing to the plates 1 and 7 respectively. This arrangement of these two rows of spring elements greatly increases the loading density of the unit and effectively makes use of the dead space occurring at each end of the unit having only one row of torsion bar spring elements as in the first-described embodiment.

Although three particular arrangements of groups of spring elements have been described in connection with the exemplary embodiments, the number, composition and orientation of the groups may be varied as desired, and also the particular form of the spring elements may difier from that hereinbefore described. Means for retaining the two plates together and preventing complete separation is, however, necessary but instead of the flexible thread or cable described, other means, such as light springs anchored to each plate for example, may be used.

I claim:

1. A spring cushioning device, in the form of a selfcontained unit interposable between an outer packaging container, and a body within the container, comprising spaced-apart first and second pressure plates relatively movable towards and away from one another, spring means between said plates, and retaining means independent of said spring means arranged to prevent complete separation of said pressure plates, said spring means comprising a plurality of resilient torsion rods associated with said first pressure plate, a first set of laterally-extending lever arms carried by the torsion rods at one end thereof and a second set of laterally-extending restraining lever arms carried by the torsion rods at the other end thereof, said first set of lever arms being directed slantingly towards said second pressure plate with their outer ends arranged to bear on the surface of said second pressure plate in slidable engagement therewith whereby movement of said pressure plates under load towards one another will deflect said first set of lever arms, thereby increasing their effective lengths and applying twisting couples to the torsion rods to generate torsional stresses therein, the opposite ends of the torsion rods being restrained from twisting in the same sense as the applied couples by said second set of laterally-extending restraining lever arms, whereby each torsion rod and its associated lever arms are formed in one piece as a single spring element from a single length of spring steel wire, and wherein individual spring elements comprise a pair of torsion rods which extend laterally with respect to one another, each torsion rod in each pair serving as the restraining lever arm of the other torsion rod, and wherein the spring elements are assembled in a plurality of groups within which corresponding torsion rods are arranged side by side.

2. A spring cushioning device according to claim 1 wherein the groups of spring elements are arranged with various orientations.

3. A spring cushioning device, in the form of a selfcontained unit interposable between an outer packaging container and a body within the container, comprising spaced-apart first and second pressure plates relatively movable towards and away from one another, spring means between said plates, and a retaining flexible strand extending between said plates to prevent complete separation thereof, said spring means comprising a plurality of spring elements each consisting of a single length of spring steel wire providing two arms extending laterally to one another and constituting torsion rods joined at their inner ends and two lever arms continuous with the outer ends of said torsion rods and extending transversely thereto,

said spring elements being arranged in groups with the torsion rods supported by and lying in a plane parallel to said first pressure plate and the lever arms associated therewith being directed slantingly towards said second pressure plate with their outer ends bearing on the surface thereof in slidable engagement therewith whereby movement of said pressure plates under load towards one another will deflect said lever arms thereby increasing their effective lengths and applying twisting couples to the torsion rods and generating torsional stresses therein.

References Cited in the file of this patent UNITED STATES PATENTS Saladee -Jan. 5, 1875 Hershey Mar. 28, 1871 Dudley Oct. 8, 1872 Perry July 29, 1890 Ross Mar. 1, 1955 

